Screw thread vials and closures are commonly used in laboratory applications for which effective sealing with near zero evaporation is important. When using conventional vial and closure assemblies, a user must be careful to apply a correct amount of torque when securing the closure to the vial. If a user fails to apply the correct amount of torque, then the assembly may fail to perform properly due to a non-uniform seal formed between the vial and closure. That is, fluids and/or vapors may escape from the vial via spillage and/or evaporation when a vapor-tight seal is not initially created or maintained.
Gas chromatography and high performance liquid chromatography applications are examples of laboratory techniques for which vapor-tight vial and closure assemblies are essential. The closures of chromatography vials often comprise a closure fitted with a piercable septum. When the closure is tightened onto the vial, the septum is compressed between the top wall of the closure and the rim of the vial to provide an essentially vapor-tight compression seal. Chromatography vials are often very small, such as 9 mm or 12 mm for example, and are typically constructed of glass or plastic.
Most solvents used in chromatography have a low vaporization point. It is important to have an effective compression seal against evaporation of the solvents used in gas chromatography and in high performance liquid chromatography applications. Particularly due to the small size of chromatography vials, it is oftentimes difficult to apply a consistent amount of torque to a plurality of closure and vial assemblies, i.e., from one to the next, particularly when multiple operators are handling the plurality of assemblies. If a closure is tilted in relation to the vial, a non-uniform or ineffective seal may occur with the vial rim that permits solvent evaporation. Even small amounts of evaporation may greatly affect the concentration of one or more solutes in the low volumes of solvent contained within the small vials. Moreover, tilting of the closure may complicate handling of the vial by robotic handling systems used in conventional autosamplers which are generally designed for a vial that has a cylindrical shape.
Another common problem with conventional chromatography vials provided with closures having piercable septums is that over-tightening of the closure with respect to the vial may result in at least a partial extrusion of the septum away from the sealing surfaces. This further reduces the likelihood of creating an effective fluid and vapor tight seal.
Vial and closure assemblies used for chromatography must also be capable of fully resealing after the septum is initially punctured. That is, when a needle penetrates and is withdrawn from the septum, the septum must resist being pushed through or being withdrawn from the cap. Such extrusion or withdrawal causes the seals to fail, increases the loss of solvent through evaporation and, thus, renders inaccurate results in chromatography applications using these vials of solvents.
Furthermore, over-torquing the closure with respect to the vial may create non-uniform, radial tension on the septum so that the septum does not present a generally planar piercing surface. This increases the risk of septum coring and/or needle bending in chromatography or autosampler instruments.
Because conventional vial and closure assemblies have not provided satisfactory solutions to the problems associated with creating an effectively vapor-tight seal, there remains a need for a vial and closure assembly that is capable of forming a vapor-tight seal, even while resisting an application of excessive torque or non-uniform seal between the vial and the closure, particularly for small vials.